Chronic beryllium disease (CBD) is a granulomatous disorder which occurs in one to five percent of individuals exposed to beryllium usually in the workplace. The lung is the predominant organ affected, with noncaseating granulomas and the accumulation of CD4+ T cells. Bronchoalveolar lavage (BAL) fluid from CBD patients demonstrates CD4+ T cells which have been selectively activated and have the ability to proliferate in response to beryllium sulfate (BeSO4) in culture. Studies from our laboratory have found alterations in the T cell receptor (TCR) gene expression in the BAL compared to blood of CBD patients. In particular, five CBD patients demonstrated CD4+ T cell expansions expressing Vbeta3. Sequencing the TCR beta-chain (TCRB) and alpha-chain (TCRA) junctional regions expressed in BAL CD4+ T cells demonstrated clonal T cell expansions. Clones from different patients were found to express nearly identical TCRs. We hypothesize that these expanded CD4+ T cell clones are responding to beryllium-peptide complexes in the lungs of patients and are important in the pathogenesis of disease. Studies are proposed to confirm that these T cell clones are selectively expanded in CBD patients and therefore not present in the lungs of healthy control subjects or patients with other granulomatous disorders. We will also study BAL in CBD patients at subsequent times of disease progression for the continued presence of these T cell clones. Using patch testing to BeSO4 in these same patients, we will determine whether similar TCRs are used by CD4+ cells infiltrating the skin. The TCR of in vivo clonal expansions will also be compared to TCR expressed by BAL and blood T cells after stimulation with BeSO4 in vitro. Separate studies will focus on the mechanism in which beryllium-reactive CD4+ T cells in CBD patients recognize antigen resulting in stimulation. CD4+ T cell hybridomas expressing the TCR of particular T cell clonal expansions in CBD patients will be used to analyze the response to BeSO4 and determine whether responses are restricted by particular self class II major histocompatibility complex (MHC) molecules. Additional studies will examine whether antigen processing is required for stimulation of these T cell hybridomas. Together, these studies will provide new insight into the immunopathogenesis of CBD and other granulomatous disorders.